One-piece flexure for small magnetic heads

ABSTRACT

A gimbal formed integral with a load beam by through etching a H pattern at the end of the beam to define a pair of tabs connected by a pair of beams; half etching from the head direction one tab with an defined area masked to form a load button; and half etching the beam from the other direction to provide the proper gimbal stiffness. In practice, the head is glued to the other tab and load is applied through the button.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates generally to the field of rigid disc drivedata storage devices and more particularly to a one-piece flexureassembly for supporting the read/write heads of the disc drive.

[0003] 2. Brief Description of the Prior Art

[0004] Disc drives of the type known as “Winchester” disc drives arewell known in the industry. Such disc drive data storage devicestypically contain a stack of rigid discs coated with a magnetic mediumon which digital information is stored in a plurality of circularconcentric tracks. The storage and retrieval of data—also called“writing” and “reading”, respectively—is accomplished by an array ofheads, usually one per disc surface, which are mounted on an actuatormechanism for movement from track to track. The most common form ofactuator used in the current generation of disc drive products is therotary voice coil actuator, which uses a voice coil motor (VCM) coupledvia a pivot mechanism to the heads to access data on the disc surfaces.The structure which supports the heads for this movement is referred toas a head/gimbal assembly, or HGA.

[0005] The HGA in a typical disc drive consists of three components:

[0006] 1. a slider, which features a self-acting hydrodynamic airbearing and an electromagnetic transducer for recording and retrievinginformation on a spinning magnetic disc. Electric signals are sent toand received from the transducer via very small twisted copper wires;

[0007] 2. a gimbal, which is attached to the slider and is compliant inthe slider's pitch and roll axes for the slider to follow the topographyof the disc, and is rigid in the yaw and in-plane axes for maintainingprecise slider positioning, and;

[0008] 3. a load beam, which is attached to the gimbal and to a mountingarm which attaches the entire assembly to the actuator. The load beam iscompliant in the vertical axis to, again, allow the slider to follow thetopography of the disc, and is rigid in the in-plane axes for preciseslider positioning. The load beam also supplies a downward force thatcounteracts the hydrodynamic lifting force developed by the slider's airbearing.

[0009] Since the introduction of the first Winchester disc drive, thephysical size of the slider has been progressively reduced, first fromthe original Winchester head to the so-called “mini-Winchester”, andmore recently to the 70 and 50 Series heads, which are 70% and 50% thesize, respectively, of the mini-Winchester slider. While these sizereductions are significant, the overall vertical dimension of the HGAhas been dictated more by the slider-supporting mechanism than by thesize of the slider itself.

[0010] The load beam and gimbal comprise an assembly generally known asa head suspension, head flexure, or simply a flexure. An example of sucha flexure is described in U.S. Pat. No. 4,167,765.

[0011] Historically, the gimbal and load beam are fabricated discretely.The gimbal and load beam pieces are realized by chemically etching 300series stainless steel foil into the desired shape, and then the twopieces are attached by means of laser welding.

[0012] The general technology trend in disc drive data storage devicesis continual shrinking of the physical size of the product whileproviding increased data storage capacity. The down-sizing of theproduct has required smaller components, especially the principalcomponents such as discs, sliders and flexures. Additionally, disc drivedesigners seek to add capacity to their designs by incorporating as manydiscs as possible within defined package dimensions. As the number ofdiscs in the unit increases, the spacing between the discs decreases,thus further driving the need for smaller sliders and flexures.

[0013] Another industry trend is to provide the user of disc drives withhigh data storage capacity at low cost. This requires developingimproved data recording technology and finding lower cost ways ofmanufacturing the components of the disc drive.

[0014] The use of discrete gimbal and load beam components laser weldedtogether, as shown in the '765 patent, has become problematic in discdrives of the current 2.5″, 1.8″ and 1.3″ generations of disc drives. Insuch units, the flexures must become thinner in order to allow desirableclose spacing of the discs, while the overlapping required to laser weldtwo discrete components necessitates increased thickness in the flexure.

[0015] Furthermore, the use of thinner gimbal and load beam componentsincreases the likelihood of residual stress caused by the laser weldingof the two components together. It has been found that laser weldingproduces residual tensile stress in the material local to the welds.This causes the flexure to distort. In the longitudinal direction, theflexure curls from the residual weld stress, and this makes it moredifficult to fit the flexure between closely spaced discs during themanufacturing process. Further, if the welds are not placedsymmetrically about the centerline of the flexure, the residual weldstress will cause a torsional distortion, or twisting, of the flexure.Such an flexure is undesirable since the twist will create a moment, ortorque, on the slider's air bearing, causing unwanted changes in theflying attitude of the head, and potentially rendering the assemblyunusable.

[0016] The welding process is also a substantial portion of the laborthat goes into the manufacture of a flexure, and it would, thus, beadvantageous to eliminate the practice of making discrete gimbals andload beams and welding the two together for cost reduction.

[0017] Since the gimbal and load beam components must overlap inflexures of existing art, the emphasis on reducing the thickness of theflexure assembly has most often focused on reducing the thickness of theindividual gimbal and load beam components. The thickest area of theload beam is the region known as the rigid beam, which usually featuresflanges along the outer edge along the longitudinal axis of the flexure.U.S. Pat. No. 4,996,616 teaches how a pair of drawn ribs can providereinforcement of the rigid beam section of the flexure. Unfortunately,the drawn pair of ribs of '616 requires that the flexure material bestrained to exceedingly high levels. Such stain can introduce cracks inthe drawn material, and high stresses in the material near the ribs.

[0018] Various attempts have been made to solve the problems inherent inwelding a gimbal and load beam together by devising a flexure in whichthe gimbal and load beam are formed from a single piece of material andwould thus require no welding. An example of such an integrated gimbaland load beam is presented in U.S. Pat. No. 4,245,267. A second exampleis known as the HTI Type 16, or T16, manufactured by HutchinsonTechnology, Incorporated. Both of these flexures have a gimbalincorporated into the load beam and, of course, no gimbal-to-load beamwelds. Both include a bonding surface on which adhesive is placed tosecure attachment of the slider to the flexure. A plurality of beams,etched into the load beam, connects this bonding surface to the loadbeam portion of the flexure and provides the desired gimbalcharacteristics.

[0019] One failing of the flexure of the '267 patent and the T16 flexurerelates to an element of flexure design commonly referred to as “loadpoint”. Simply stated, load point refers to the single point of contactwhere the downward force of the load beam is applied to the slider.Proper selection of this load point ensures that the forces related tothe hydrodynamic air bearing of the slider are properly balanced. Inprior art flexures such as the one described in the '765 patent, loadpoint is developed by forming an upward-extending dimple in the gimbalbonding surface. The load beam contacts the spherical surface of thisdimple at a single point to allow proper gimbal action. In the case ofthe '267 and T16 flexures, however, a well defined load point is notprovided, and, thus, an undesirably wide range of variation in sliderflying characteristics is associated with these types of flexure.

[0020] A second fundamental problem with the '267 and T16 types offlexures is that the downward force of the load beam is applied to theslider by placing the gimbal beams into bending mode, and the gimbalbeams must therefore be stiff in bending mode. These same gimbal beams,however, must be compliant in bending mode to allow the propergimballing action. This conflicting requirement results in designs thateither work poorly as a gimbal or become deformed under load.

[0021] A third problem with the '267 and T16 flexures is that the sliderbonding surface, in general, covers a large area over the center of theslider. The slider is attached to the flexure with an adhesive epoxy,and, in order to reduce the cure time of the adhesive, the assembly isusually heated in an oven. Since the slider and flexure are made ofdissimilar materials with different coefficients of linear thermalexpansion, thermally induced strains develop at the bond when theassembly cools. These strains can distort the slider and undesirablychange the flatness of the air bearing surface of the slider, thus, onceagain, introducing unacceptably wide variation into the flyingcharacteristics of the heads.

[0022] A need clearly exists for an improved slider-supporting flexurewhich reduces the overall vertical height of the HGA, and which can bemanufactured in a simple, cost-effective manner.

SUMMARY OF THE INVENTION

[0023] The flexure of the present invention is a one-piece loadbeam/gimbal assembly formed from a single piece of material. Featuresfor providing the gimballing action, bonding of the slider to theflexure and location of the load point are all created using theprocesses of etching and half-etching. In the preferred embodiment, thegimbal end of the flexure is substantially rectangular, and a generallyH-shaped opening is symmetrically located within the rectangular shape.The side rails formed between the H-shaped opening and the side edges ofthe gimbal are half-etched to reduce their thickness, and these siderails act as the gimballing mechanism of the flexure. A pair of tabs isformed in the gimbal end of the flexure on either side of thecross-member of the H-shaped opening, and one of these tabs is alsohalf-etched to reduce its thickness. The full-thickness tab is used tobond the slider to the flexure, while the other tab serves to locate aload point contact which is formed by not half-etching in the desiredlocation for the load point. The load beam portion of the flexure isstiffened by forming side rails or channels along the sides of the loadbeam portion of the flexure and by forming a tear-drop-shapedindentation in the load beam. Both the side rails and indentation areformed toward the side of the flexure on which the slider is mounted.

[0024] It is an object of the invention to provide a low-height flexurefor mounting and supporting a slider.

[0025] It is another object of the invention to provide a flexurewherein the gimbal and load beam elements are formed from a single pieceof material, and require no welding.

[0026] It is another object of the invention to provide a flexure whichis simple and inexpensive to manufacture.

[0027] It is another object of the invention to provide a flexure whichincorporates a load point which is well defined and simple to locate atan optimized location.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The features, benefits and objects of the invention can be bestunderstood from the following detailed description of the invention whenread in conjunction with the following drawings.

[0029]FIG. 1 is a plan view of a disc drive data storage device in whichthe present invention is particularly useful.

[0030]FIG. 2 is a plan view of the preferred embodiment of the flexureof the present invention.

[0031]FIG. 3 is a detailed view of the gimbal portion of the flexure ofFIG. 2.

[0032]FIG. 4 is a sectional view of the gimbal portion of the flexure ofthe present invention.

[0033]FIG. 4A is a sectional view of the gimbal portion of the flexureof the present invention as assembled to a slider and in cooperativearrangement with a disc.

[0034]FIG. 5 is a partial sectional view showing the forming of the edgeof the rigid beam portion of the flexure of the present invention.

[0035]FIG. 6 is a partial sectional view showing the forming of therigid beam to increase stiffness.

[0036]FIG. 7 is a partial perspective view of the flexure of the presentinvention as assembled to a slider assembly.

DETAILED DESCRIPTION OF THE INVENTION

[0037] Referring now to the drawings and more specifically to FIG. 1,shown is a disc drive 2 in which the present invention is particularlyuseful. The disc drive 2 includes a base member 4 which, in cooperationwith a top cover 6 (shown in partial cutaway), forms a sealedenvironment to protect the delicate internal components from outsidecontaminants. A number of rigid discs 8 coated with a magnetic mediumare mounted for rotation on a spindle motor (shown generally at 10). Thesurfaces of the discs 8 hold a large number of concentric circulartracks to which information is written and from which information isread. These tracks are represented by the innermost and outermosttracks, designated by broken lines 12 and 14 respectively.

[0038] An actuator body 16 is adapted for rotation about a pivot shaft18 by a voice coil motor (VCM), shown generally at 20. On the side ofthe actuator body 16 opposite the VCM 20 are a number of head mountingarms 22 to which are attached a plurality of flexures 24 for themounting of sliders 26. Power for the VCM 20, as well as the signalsused to read and write data, is passed via a printed circuit cable (PCC)28.

[0039] Turning now to FIG. 2, shown is a plan view of a flexure 30 madein accordance with the present invention. The flexure 30 is symmetricalabout a longitudinal axis 31 and is made up of four distinct majorareas:

[0040] 1. a gimbal/slider mounting area 32;

[0041] 2. a rigid beam 34;

[0042] 3. a pair of compliant beams 36, and;

[0043] 4. an attachment surface 38.

[0044] The entire flexure 30 is formed from a single piece of 300 seriesfull hard stainless steel, preferably 0.0025 inches in thickness, andmanufactured using well known chemical etching processes.

[0045] A pair of alignment holes 40, 42 aid in fixturing the flexureduring the process of bonding the slider (not shown).

[0046] The attachment surface 38 in the example of FIG. 2 is shaped tobe attached to a particular type of mounting plate to provide a strongsurface for attachment of the entire flexure head assembly to the headmounting arms 22 of the actuator body 16. While the specific method ofmounting the flexure is not considered a part of this invention, itshould be noted that this attachment surface 38 could easily be adaptedfor use with other types and designs of mounting apparatus.

[0047] The direction of movement of the disc relative to the flexure isshown by arrow A. Any slider attached to the flexure of the presentinvention is therefore assumed to have its leading edge closest to theattachment surface 38 and its trailing edge closest to the free end ofthe gimbal/slider mounting area 32.

[0048] The gimbal/slider mounting area 32, the rigid beam 34 and thepair of compliant beams 36 will each be discussed in turn below.

[0049]FIG. 3 shows a detailed view of the gimbal/slider mounting area 32of the flexure of the present invention with a slider 48 attached. Aswas previously mentioned, the flexure of the present invention is formedby the process of chemical etching. In usual chemical etching processes,the material to be etched is first coated on both sides with a materialcalled resist. The resist is patterned using a stencil and exposing theresist to a light source. Unexposed resist is then stripped away,leaving exposed metal that will be etched away in the presence of anacid-like etchant. Both sides of the material are treated in thismanner, with the pattern on both sides being very accurately aligned.This is the process used to define the perimeter outline of the flexureof the present invention and all through openings.

[0050] In half-etching, the pattern of the stencil on one side of thematerial is dissimilar to that on the other side. This also is a wellknown technique for etching text, art or half-tone photographs intosheet metal. It is known that if the area to be half-etched islarge—that is, it has a length or diameter many times that of thematerial thickness—the depth of the half-etching will be approximatelysixty percent that of the material thickness.

[0051] The process of full- and half-etching is used to produce severalof the features of the flexure of the present invention. For instance,as can be seen in FIG. 3, an H-shaped opening 44 has been etchedcompletely through the material, and areas beside the vertical legs andon one side of the cross member of the H-shaped opening 44 have beenhalf-etched. Specifically, the area shaded lower-left-to-upper-right ishalf etched on the near side of the material, while the area shadedlower-right-to-upper-left has been half-etched on the far side of thematerial. Since the overall thickness of the material is approximately0.0025 inches, these half-etched areas are reduced in thickness to about0.0010 inches thick.

[0052] This half-etching process forms a pair of gimbal beams 58 whichwill be discussed in detail below.

[0053] The etching process also forms a slider mounting tab 46 to whichthe slider 48 is adhesively bonded. As can be seen in the figure, thisbonding is thus done only in that area of the slider 48 closest to thetrailing edge of the slider 48. In prior art flexures, such as theflexure of the '765 patent, the bonding surface was generally centeredon the slider and occupied a large percentage of the entire top surfaceof the slider. The location of the bonding surface in the flexure of thepresent invention has several advantages:

[0054] 1. In prior art flexures, the air bearing surface distortioncreated by thermal strain during oven curing of the adhesive wassignificantly large, since the bonding was done in the center of theslider and over a relatively large area of the slider. In general, thesmaller the bonding surface and the farther the bonding surface isremoved from the center of the slider, the lower the amount of airbearing distortion caused by oven curing of the adhesive. With theflexure of the present invention, the bonding surface is located as faras possible from the center of the slider—in fact, with a 50% slider,the bonding surface includes only that area within approximately 0.025inches of the trailing edge of the slider—thereby providing minimal airbearing surface distortion.

[0055] 2. The flexure of the present invention provides great ease ofinspection of the adhesive bond between the slider and the flexure. Inprior art flexures, the bonding surface is located between the sliderand a separate load beam. The load beam obstructs the view of thebonding surface, which makes it difficult, if not impossible, to confirmthe presence of adhesive fillets around the entire perimeter of thebonding surface. In the flexure of the present invention, no such visualobstruction exists.

[0056] 3. The structure of the flexure of the present inventionfacilitates conductive heating of the bonding surface to speed thecuring of the adhesive. In prior art flexures, the adhesive that securesthe slider to the flexure was typically heated in a convective oven tohasten adhesive curing. Conductive heating, also known as “hot footbonding” can substantially reduce the curing time, but was generally notpractical in prior art flexures since the load beam prevented directaccess to the bonding surface. In the flexure of the present invention,the bonding surface is completely accessible for conductive heating,thus potentially reducing the time required to cure the adhesivesecuring the slider to the flexure.

[0057] 4. The flexure of the present invention also provides for greaterbond strength than could be realized in prior art flexures. For avariety of reasons, the bonding surface of prior art flexures could notextend over the full width of the slider. Since, in general, the widerthe bond, the greater the bond strength, and since the inventive flexureallows the bond to extend across virtually the entire slider, theflexure of the present invention can be expected to provide the maximumbond strength for a given size of slider.

[0058] The H-shaped opening 44 also forms a load point tab 50 on theopposite side of the cross-member of the opening from the slidermounting tab 46. The load point tab 50 transmits the load force of theflexure to the slider 48 via a load point button 52, or load supportingprotrusion, which is formed by masking the desired location and sizeprior to half-etching, so that the load point button 52 maintains thefull thickness of the flexure material. Since the load point tab 50 ishalf-etched on the far side of the material as viewed, this has theeffect of creating a “pin” which projects toward and contacts the top ofthe slider 48. The load point button 52 should be as small in area as ispossible given the manufacturer's capability in chemical etching. Thisdimension has been found currently to be about 0.002 inches, whichcauses the load force of the flexure to be applied to the slider at asclose as possible to a single point. The location of this single pointis selected to provide the desired flying characteristics for theparticular design.

[0059] Several significant advantages are realized by the flexure of thepresent invention over flexures of the prior art:

[0060] 1. The load point button 52 of the flexure of the presentinvention can be more exactly located relative to the slider than canthe load points of prior art flexures. In prior art flexures, the loadpoint is typically a spherical formed projection, or dimple, in theapproximate center of the slider bonding area which contacts the loadbeam at a single point at the apex of the projection. However, the exactapex of the spherical projection, and therefore the exact load point, isdifficult to determine. The exact location of the half-etched load pointbutton 52 of the flexure of the present invention is, by comparison,easy to determine.

[0061] 2. With the load point button 52 of the flexure of the presentinvention there is less variability in protrusion height. In formedprotrusions of the prior art, the tolerance on the protrusion height hastypically been ±0.0010 inches. In the flexure of the present invention,this variability has been reduced to the order of ±0.0002 inches.

[0062] 3. There is less variation in the location of the load point withthe flexure of the present invention than in prior art flexures. Inprior art flexures, the spherical protrusion is generally formed as asecondary step in the manufacturing process after the shape and size ofthe flexure have been determined by etching. This means that thelocation where the forming occurs varies with respect to the datum edgesof the flexure, since some clearance must be provided between the datumedges of the flexure and the location surfaces of the forming die. Inthe flexure of the present invention, the edge datums and load pointbutton coexist on the same artwork pattern, or mask, thus substantiallyreducing the variability in the location of this feature.

[0063] 4. The flexure of the present invention provides greaterflexibility to modify the desired location of the load point than doprior art flexures. The location of the load point relative to theslider is critical to obtain the desired flying attitude of the slider.Occasionally during the development of a new disc drive product, or themodification of an existing product, it may become necessary to changethe location of the load point. It has been economically impractical tomodify the location of the formed spherical projection of prior artflexures due to the required retooling and new fixtures. Therefore,modifications in load point location in prior art flexures havegenerally been accomplished by modifying the bonding fixtures used toalign the slider and flexure during the adhesive bonding procedure. Withthe flexure of the present invention, it is possible to change thelocation of the load point button 52 by simply changing the artworkpattern, or mask, used in the etching process. Generally speaking,master artwork patterns are far less expensive to modify than fixturesand hard tooling.

[0064] The actual shape of the load point button 52 can be easilydetermined by the artwork pattern, and can thus be round, oval or oblongshould such be desired. In some cases it may be desirable or necessaryto radius the edges of the load point button 52. This can be done byspanking the button with a suitably shaped die. An alternative methodwould be etching a half-tone transition between the top of the buttonand the full depth of the half-etching. The half-tone pattern couldconsist of small circles whose size and spacing are related to theirdistance from the center of the button, or rings whose line width andline spacing are also related to their distances from the button center.

[0065] The exact location of the load point button 52 is determined toprovide the desired flying attitude of the slider. Typically, thislocation is a few thousandths of an inch away from the center of theslider toward the trailing edge. The desired load point is alsofrequently offset from the longitudinal centerline of the slider tocompensate for velocity vector field variations and such known factorsas the torsional bias applied by the tiny wires used to carry read/writesignals to and from the head. If such an offset in load point locationis incorporated in the artwork pattern, it can be extremely difficult todetermine the direction of this offset visually. Such a determination isnecessary because flexures intended for use on opposite sides of thediscs would typically have this offset in opposite directions.Therefore, the artwork pattern can include an offset determination hole54 which would be located at an obviously assymmetrical location andwould indicate toward which side of the flexure the load point button 52was offset.

[0066] Another feature of the flexure of the present invention is aslider alignment inspection hole 56. This slider alignment inspectionhole 56 may be round or elongated as shown in the figure. Such a featureis desirable when measuring the alignment of the slider to the flexurewith a vision based metrology system. Such measuring systems depend onhigh contrast at edge locations, and a through hole will allow a portionof the slider edge to be silhouetted by a profile light source when theslider is properly aligned with the flexure.

[0067]FIG. 3 also shows a pair of gimbal beams 58 formed adjacent thevertical legs of the H-shaped opening 44. It should be recalled thatthese gimbal beams 58 were half-etched on the near side of the materialas viewed in FIG. 3 to a thickness of approximately 0.0010 inches. Sincethe slider 48 is bonded to the slider mounting tab 46, and load force isapplied to the slider 48 through the load point button 52 on the loadpoint tab 50, it will be apparent to one skilled in the art that thegimbal beams 58 will allow the necessary gimballing action of theflexure while still maintaining needed stiffness in the desired axes. Toensure proper operation of the gimbal beams 58, it is desirable to havethe plane of the gimbal beams 58 coincident with the point of contact ofthe load point button 52 with the slider 48. This is best achieved inthe flexure of the present invention when the half-etching of the gimbalbeams 58 and the load point tab 50 are on opposite sides of thematerial. In some instances, it may be desirable to introduce someforming of the load point tab 50, since this tab is subject to somedeflection when under load. The amount of deflection of the load pointtab 50 can be found using the following formula: $\begin{matrix}{{deflection} = \frac{4\quad F\quad L^{3}}{E\quad W\quad T^{3}}} & (1)\end{matrix}$

[0068] where:

[0069] F is the load force

[0070] L is the distance from the load point button to the root of theload point tab;

[0071] E is the modulus of elasticity of the flexure material;

[0072] W is the width of the load point tab at its root, and;

[0073] T is the thickness of the load point tab.

[0074] The slope at the end of the load point tab can be found using theformula: $\begin{matrix}{{slope} = \frac{6\quad F\quad L^{3}}{E\quad W\quad T^{3}}} & (2)\end{matrix}$

[0075] Using algebra, it is possible to show that the end of a deflectedbeam can be made tangent to the root of the beam if the beam is formedat a point one-third the length of the beam from the base of the beam.

[0076] The preferable method of forming the single bend in the loadpoint tab 50 is by stamping. In volume manufacturing, it may benecessary, due to variation in material thickness and half-etch depths,to overbend and then relax back to the desired angle using, forinstance, infrared heating.

[0077] An example of the calculations to determine the design of theload point tab follows.

[0078] Assume:

[0079] Load point is offset 0.005″ from center of slider toward thetrailing edge.

[0080] Half length of the slider is 0.040″.

[0081] Clearance (end of slider to end of tab) is 0.005″.

[0082] Tab base width is 0.058.

[0083] Tab length (L) (base to load point) is0.005″+0.040″+0.005″=0.050″

[0084] Load force (F) is 3 grams.

[0085] Deflection under load at the load point can be found using thefollowing formula: $\begin{matrix}\frac{\quad {F\quad L^{3}}}{3E\quad I} & (3)\end{matrix}$

[0086] where I is the bending moment of inertia.

[0087] Solving the equation with the above assumptions:

[0088] Slope under load at the load point can be found using the$\frac{3 \cdot \left( {2.204622/1000} \right) \cdot \left( {.050}^{3} \right)}{3 \cdot (27.6) \cdot 10^{6} \cdot \frac{1}{12} \cdot ({.058}) \cdot \left( {.001}^{3} \right)} = {{.002066}\quad {inches}}$

[0089] following formula: $\begin{matrix}\frac{F\quad L^{2}}{2\quad E\quad I} & (4)\end{matrix}$

[0090] Solving equation (4) with the above assumptions:$\frac{3 \cdot \left( {2.204622/1000} \right) \cdot \left( {.050}^{2} \right)}{3 \cdot (27.6) \cdot 10^{6} \cdot \frac{1}{12} \cdot ({.058}) \cdot \left( {.001}^{3} \right)} = {{.061974} = {3.546\quad {^\circ}}}$

[0091] Therefore, if the load point tab 50 is preformed with a 3.546°bend at a point one-third of the distance from the base of the tab tothe load point button 52, it can be assumed that the actual contactpoint between the load point button 52 and the slider 48 will liesubstantially in the plane of the gimbal beams 58 when the assembly isunder designed load conditions.

[0092] Referring now to FIG. 4, the desired forming of the load pointtab 50 is illustrated by a detail sectional view taken along line 4-4 ofFIG. 3. As can be seen, the load point tab 50 is bent in the directionof the slider (not shown) at an angle of approximately 3.546°. Becauseof this bending, when the slider is mounted on the slider mounting tab46, and the entire assembly is brought into its intended relationshipwith the spinning disc of the disc drive, the bottom of the load pointbutton 52—and thus the top surface of the slider—will lie substantiallyin the plane occupied by the gimbal beams 58. This relationship is bestseen in FIG. 4A, wherein a slider 48 has been bonded to the slidermounting tab 46 and the entire assembly brought into operationalrelationship to a disc 8.

[0093] Similarly, various characteristics of gimbal beam stiffness canalso be calculated.

[0094] Assume:

[0095] L (length of the gimbal beams)=0.106″.

[0096] r (distance from the load point button contact to the gimbal beamtrailing edge)=0.053″.

[0097] w (width of one gimbal beam)=0.010″.

[0098] t (thickness of the gimbal beam)=0.001″.

[0099] The stiffness of the gimbal can be calculated in various axesusing the following formulae:${{Pitch}\quad {stiffness}} = {{\frac{2E\quad I\quad r}{L}\left( {\frac{6\quad r}{L^{2}} + \frac{2}{r} - \frac{6}{L}} \right)} = {{\frac{2 \cdot (27.6) \cdot 10^{6} \cdot \frac{1}{12} \cdot 2 \cdot ({.010}) \cdot \left( {.001}^{3} \right) \cdot ({.053})}{.106}\left( {\frac{6 \cdot {.053}}{{.106}^{2}} + \frac{2}{.053} - \frac{6}{.106}} \right)} = {{{.00434}\quad \frac{\text{inch-lb}}{rad}} = {{.197}\quad \frac{\quad \text{inch-gram}}{rad}}}}}$${{Roll}\quad {stiffness}} = {{\frac{E\quad w\quad t^{3}}{3\left( {1 + \upsilon} \right)L}{where}\quad \upsilon \quad {is}\quad {{Poisson}'}s\quad {ratio}} = {\frac{27.6 \cdot 10^{3} \cdot {.010} \cdot {.001}^{3}}{3{\left( {1 + {.305}} \right) \cdot {.106}}} = {{{.001330}\quad \frac{\text{inch-lb}}{rad}} = {{.603}\quad \frac{\text{inch-gram}}{rad}}}}}$${{Yaw}\quad {stiffness}} = {{\frac{2E\quad I\quad r}{L}\left( {\frac{6r}{L^{2}} + \frac{2}{r} - \frac{6}{L}} \right)} = {{\frac{{2 \cdot 27.6 \cdot 10^{6} \cdot \frac{1}{12} \cdot \left( {{.090}^{3} - {.070}^{3}} \right) \cdot {.001} \cdot {.053}}\quad}{.106}\left( {\frac{6 \cdot {.053}}{{.106}^{2}} + \frac{2}{.053} - \frac{6}{.106}} \right)} = {8.375\quad \frac{\quad \text{inch-lb}}{rad}}}}$${{Across}\quad {track}\quad {stiffness}} = {\frac{24\quad E\quad I}{L^{2}\left( {{2L} - {3r}} \right)} = {\frac{24 \cdot 27.6 \cdot 10^{6} \cdot \frac{1}{12} \cdot {.001} \cdot {.010}^{3}}{{.106}^{2}\left( {{2 \cdot {.106}} - {3 \cdot {.053}}} \right)} = {92.694\quad \frac{lb}{inch}}}}$${{Along}\quad {track}\quad {stiffness}} = {{\frac{{E2}\quad w\quad t}{L}\quad \frac{27.6 \cdot 10^{6} \cdot 2 \cdot {.010} \cdot {.001}}{.106}} = {5208\quad \frac{lb}{inch}}}$${{Stiction}\quad {stress}} = {\frac{1}{2\quad w\quad t} = {\frac{2.204622/1000}{2 \cdot {.010} \cdot {.001}} = {110.231\quad \frac{psi}{gram}}}}$

[0100] An analysis of these stiffness figures reveals that the gimbal isrelatively compliant in the pitch and roll axes, as is desireable forfollowing minor variations in the surface of the disc, while it is verystiff in the yaw axis, since any compliance in yaw would result inmisalignment of the head from the desired on track position. Similarly,the across-track stiffness and along track stiffness are very high tomaintain on-track stability.

[0101] It should be noted that the stiction stress calculation isnormalized to one gram of stiction force, and since the yield stresslimits of the materials envisioned is on the order of 200,000 psi, onlyan amount of stiction which would be totally fatal to the entire discdrive could cause the gimbal to fracture.

[0102] It should also be noted that in the flexure of the presentinvention, the only gimbal forming required is a single bend in the loadpoint tab 50. Prior art flexures universally require forming a loadpoint protrusion, sometimes referred to as a “dimple” in the gimbalbonding surface, which invariably effected the flatness of the gimbalbonding surface. In addition, prior art flexures have some type ofoffset forming to allow the gimbal bonding surface to be out-of-planefrom the rest of the flexure by an amount equal to the dimple height.This out-of-plane forming introduces stresses and distortions into thegimbal structure, and in some instances, cracking of the gimbal canoccur. Such problems are totally absent in the flexure of the presentinvention.

[0103] An additional benefit of the gimbal of the flexure of the presentinvention is a substantial reduction in the distance between the centerof gravity of the slider body and the point of contact of the load pointprotrusion. When rapid accelerations occur in the head positioningactuator of the disc drive, some undesirable changes in flying attitudeoccur. The inertia of components such as the slider can create externalmoments on the air bearing during such events. A general rule-of-thumbis that the magnitude of these moments is directly proportional to thedistance between the center of gravity of the slider and the point ofcontact of the load point protrusion. In prior art flexures, it has notbeen possible to have the load point contact the slider and still havethe contact point coplanar with the gimbal beams, as it should be forminimal gimbal stiffness in the desired axes. Prior art flexures used adimple formed on the opposite side of the bonding surface from theslider to provide a contact point for the load beam, which meant thatthe load point was displaced from the slider by at least the height ofthe dimple. In the flexure of the present invention, the load pointbutton 52 directly contacts the slider 48.

[0104] Referring now back to FIG. 2, the rigid beam 34 portion of theflexure of the present invention is symmetrical about the longitudinalaxis 31 of the flexure and generally trapezopidal in shape with thesmall base of the trapezoid adjacent the gimbal/slider mounting area 32.The general function of the rigid beam 34 is to transfer the downwardforce generated by the pair of compliant beams 36 to the gimbal/slidermounting area 32. As such, it is important that the rigid beam 34 beextremely stiff to resist both bending along the longitudinal axis 31and twisting about the longitudinal axis 31.

[0105] In order to impart high stiffness to the rigid beam 34, thematerial of the rigid beam 34 is formed to substantially increase thesectional moment of inertia. Along the tapered edges of the rigid beam34 are V-shaped channels 60, with the apex of the V extending in thedirection of the slider. FIG. 5 is a partial sectional view of one ofthese channels 60 taken along the general line 5-5 in FIG. 2. Thechannels 60 are typically formed 0.0045 inches out-of-plane. The distaledge of the V channel may be approximately level with the plane of theunformed material as shown at 62. In some cases it may be advantageousto have the distal edge of the V channel extend beyond the plane of theunformed material, since the bending moment increases in the directionaway from the gimbal, and therefore a higher sectional moment of inertiais desirable. In such a case, the distal end of the channel could beformed at the point shown by the designator 64. In either case, theprecise location of the distal end of the channel 60 is determined bythe artwork mask used to etch the outer edge of the flexure.

[0106] A further, albeit slight, increase in sectional moment of inertiacan be realized if the distal edge of the V channel 60 is not etched ata right angle to the material surface, as is typical in prior artflexures. By using two differing artwork patterns during etching, it ispossible to etch a “beveled” edge. Ideally, the angle of this bevelshould be such that the etched edge, after forming, will besubstantially parallel to the plane of the unformed material. Thisapproach is shown in FIG. 5 at the distal edge of the channel 60. In thefigure it can be seen that the very edge of the material of the flexureis half-etched to form a “step” which, after the forming of the channel60, lies substantially parallel to the surface 66 of the unformedmaterial. This stepped edge provides the maximum “edge length”, and thuscontributes to the stiffness of the rigid beam 34.

[0107] While the preferred cross-sectional shape of the channel is a V,it should be readily apparent that other shapes could be employed toachieve a high sectional moment of inertia.

[0108] Additional stiffening of the reinforced beam can be obtained bydrawing the center section of the rigid beam 34 out-of-plane. In theplan view of FIG. 2, this stiffening area 68 is somewhat teardropshaped, and oriented in the same direction as the tapering of the rigidbeam 34, but other shapes for the stiffening area can be readilyconceived. The stiffening area 68 is drawn out-of-plane approximatelythe same amount as are the channels 60.

[0109] The rigidity of the rigid beam 34 is optimized when the area ofthe drawn material in the stiffening area 68 is substantially equal tothe area of the unformed material. As shown in FIG. 6 which is again apartial sectional view along line 5-5 of FIG. 2, between the drawn andundrawn material is a transition region 70 which is strained when thematerial is formed. In order to prevent cracking in the transitionregion 70, it has been found that the strain level should be kept to amaximum of 5 percent of material tensile strength. The minimum length,x, for a transition region 70 which meets this requirement can be foundby using the following formula: $x = \sqrt{\frac{d^{2}}{1.05^{2} - 1}}$

[0110] where:

[0111] x is the length of the transitional region, and

[0112] d is the distance out-of-plane that the material is drawn.

[0113] The channels 60 on the edges of the rigid beam 34 also serve as arouting path for the wires (not shown) which carry the read/writesignals to and from the head mounted in the slider. As can be seen inFIG. 2, the ends 72 of the channels 60 nearest the gimbal/slidermounting area 32 are formed at an acute angle to the line 74 whereforming of the channels 60 begins. This angle is to facilitate therouting of the head wires into the channels 60.

[0114]FIG. 7 is a detail perspective view of the gimbal end of theflexure of the present invention with a slider attached. As can be seen,the wires 76 that carry the read/write signals to and from thetransducer (not shown) are attached to the slider 48 on its trailingsurface 78 and are routed in a loop to the channel 60 along the side ofthe flexure. Since the flexure is symmetrical about its longitudinalaxis, this allows upward-facing and downward-facing flexures to carrythe wires 76 on the same side relative to the actuator, thus easingconnection to the pcc (28 in FIG. 1) which carries these signals to andfrom the disc.

[0115] Referring again to FIG. 2, attached to the large base of thetrapezoid shaped rigid beam 34 are a pair of compliant beams 36. Onefunction of these beams 36 is to serve as a low friction pivot, orhinge. Another function is to provide the downforce that counteracts thehydrodynamic lift of the air bearing surfaces of the slider. In thepreferred embodiment, the two compliant beams 36 are each 0.100 incheslong and 0.040 inches wide. The distance between the outer edges of thetwo compliant beams 36 is 0.200 inches at the root of the beams, withthis distance decreasing in the direction of the gimbal/slider mountingarea 32 at a rate substantially equal to the tapering of the rigid beam34. The distance from the root of the two compliant beams 36 to the loadpoint button (52 in FIG. 3) is 0.610 inches.

[0116] The two compliant beams 36 are formed after the flexure is etchedsuch that the slider will be encouraged toward the disc when the entirehead/gimbal assembly is installed in the disc drive. The preferredmethod of forming the two compliant beams 36 is described in detail inU.S. Pat. No. 5,065,268, issued Nov. 12, 1991, assigned to the assigneeof the present invention and incorporated herein by reference.

[0117] A comparison between a typical prior art flexure/slider assemblyand a flexure/slider assembly made in accordance with the presentinvention shows clearly that the inventive flexure can contributesignificantly to the reduction of separation between the flexure/slidermounting surface and the disc surface, thus allowing closer disc spacingwhich can lead to either lower overall drive height or additional discswithin a given package dimension. In prior art flexure/sliderassemblies, the minimum flexure mounting surface to disc surfacedimension is the arithmetic sum of the following thicknesses: Sliderthickness: 0.017 ± 0.001 Gimbal dimple height: 0.0055 ± 0.0005 Load beamthickness: 0.0025 ± 0.00025 Total: 0.0250 ± 0.00175 worst case, ±0.001146 three sigma.

[0118] Using the flexure of the present invention, the same minimumdimension is the sum of the following thicknesses: Slider thickness:0.017 ± 0.001 Flexure thickness: 0.0025 ± 0.00025 Total: 0.0195 ±0.00125 worst case, ± 0.001031 three sigma.

[0119] From these figures, it is apparent that, not only does theflexure of the present invention allow approximately a 22% reduction inthis dimension, but that worst case tolerance error has also beensignificantly reduced.

[0120] It is also apparent that the flexure of the present invention isless expensive to manufacture since the need for gimbal-to-load beamwelding has been eliminated. Laser welders are expensive pieces ofcapital equipment in their own right, with low throughput, and requireexpensive and precise fixturing to align the separate pieces for thewelding process. Moreover, as previously stated, the welds produced bylaser welding contain high residual stresses that can distor theflexure, reducing quality levels.

[0121] In summary, the inventive flexure can contribute to a reductionin disc-to-disc spacing—with either reduced drive height or increaseddrive capacity—while lowering costs and improving the precision of thedisc drive.

[0122] While a specific embodiment of the present invention has beendiscussed, numerous variations—for instance in materials, proportion ofelements, and methods of manufacture—are possible. For example, theflexure of the present invention could be realized from beryllim copperor titanium, the flexure could be made proportionally wider to improvein-plane bending resonant frequency, or the flexure could bemanufactured by stamping with reactive etching to reduce the thicknessof material in desired areas.

[0123] It will be clear that the present invention is well adapted tocarry out the objects and attain the ends and advantages mentioned aswell as those inherent therein. While a presently preferred embodimenthas been described for purposes of this disclosure, numerous changes maybe made which will readily suggest themselves to those skilled in theart and which are encompassed in the spirit of the invention disclosedand as defined in the appended claims.

What is claimed is:
 1. A flexure for a slider for magnetic recording,the slider supported against a fluid bearing generated by relativemotion between the slider and a moving magnetic surface, said flexurecomprising A) a mounting surface to attach the flexure to a mountingplate or a head positioning support arm, B) a pair of compliant beamshaving first and second ends, the beams attached to the mounting surfaceat the first ends, the beams lying substantially parallel to alongitudinal centerline of the flexure being formed out of plane toprovide a load force to react against hydrodynamic lifting forcegenerated by the fluid bearing of the slider, C) a reinforced rigid beamattached to the second ends of the compliant beams, the rigid beam beingof high bending stiffness to transfer the load force of the compliantbeams to the slider with negligible distortion along the length of therigid beam, D) a gimbal section attached to the rigid beam opposite thecompliant beams, the gimbal section being substantially rectangular inshape and having an H-shaped opening with the two vertical legs of the Hsubstantially parallel to the longitudinal centerline of the flexure anda cross member connecting the two vertical legs, the H-shaped openingdefining a rectangular slider mounting tab between the vertical legs ofthe H-shaped opening and on the side of the cross member of the H-shapedopening farthest from the rigid beam, the H-shaped opening defining arectangular load point tab between the vertical legs of the H-shapedopening and on the side of the cross member of the H-shaped openingclosest to the rigid beam, the load point tab being of reduced materialthickness and having a load supporting protrusion located closelyadjacent the cross member of the H-shaped opening, and the flexuremounting surface, compliant beams, rigid beam and gimbal section allformed from a single contiguous piece of resilient material.
 2. Aflexure as claimed in claim 1 wherein one surface of the load point tabis continuous with the corresponding surface of the rigid beam and theother surface of the load point tab is discontinuous with thecorresponding surface of the rigid beam.
 3. A flexure as claimed inclaim 2 wherein the load supporting protrusion on the load point tab israised above the load point tab surface that is discontinuous with thecorresponding surface of the rigid beam.
 4. A flexure as claimed inclaim 3 wherein the load supporting protrusion is realized by formingthe material of the load point tab.
 5. A flexure as claimed in claim 3wherein the load supporting protrusion is realized by isolating an areafrom the process used to reduce the thickness of the load point tab. 6.A flexure as claimed in claim 5 wherein the plan view shape of the loadsupporting protrusion is substantially circular.
 7. A flexure as claimedin claim 5 wherein the plan view shape of the load supporting protrusionis substantially elliptical.
 8. A flexure as claimed in claim 5 whereinthe plan view shape of the load supporting protrusion is substantiallyoblong.
 9. A flexure as claimed in claim 5 wherein the plan view shapeof the load supporting protrusion is irregular in shape.
 10. A flexureas claimed in claim 1 wherein the load supporting protrusion is locatedon the longitudinal centerline of the flexure.
 11. A flexure as claimedin claim 1 wherein the load supporting protrusion is offset from thelongitudinal centerline of the flexure.
 12. A flexure as claimed inclaim 11 including offset determination means for visually indicatingthe direction in which the load supporting protrusion is offset from thecenterline.
 13. A flexure as claimed in claim 12 wherein the offsetdetermination means is integral to the flexure.
 14. A flexure as claimedin claim 12 wherein the offset determination means is a hole located onthe same side of the centerline. as the load support protrusion.
 15. Aflexure as claimed in claim 3 wherein the load point tab is formedout-of-plane in the direction of the slider to such an extent that, whenthe attached slider is brought into cooperative arrangement with thesurface of the disc, the load support protrusion will lie substantiallyin the same plane as the rigid beam.
 16. A flexure as claimed in claim 2wherein the material between the vertical legs of the H-shaped openingand the outer extreme of the gimbal section is of reduced materialthickness.
 17. A flexure as claimed in claim 16 wherein one surface ofthe material between the vertical legs of the H-shaped opening and theouter extreme of the gimbal section is smooth and continuous with onesurface of the rigid beam and the other surface of the material in thesame location is discontinuous with the surface of the rigid beam. 18.An assembly for magnetic recording on a magnetic surface, the assemblymade up of a flexure comprising A) a mounting surface to attach theflexure to a mounting plate or a head positioning support arm, B) a pairof compliant beams having first and second ends, the beams attached tothe mounting surface at the first ends, the beams lying substantiallyparallel to a longitudinal centerline of the flexure and being formedout of plane to provide a load force to react against hydrodynamiclifting force generated by the fluid bearing of the slider, C) areinforced rigid beam attached to the second ends of the compliantbeams, the rigid beam being of high bending stiffness to transfer theload force of the compliant beams to the slider with negligibledistortion along the length of the rigid beam, D) a gimbal sectionattached to the rigid beam opposite the compliant beams, the gimbalsection being substantially rectangular in shape and having an H-shapedopening with the two vertical legs of the H substantially parallel tothe longitudinal centerline of the flexure and a cross member connectingthe two vertical legs, the H-shaped opening defining a rectangularslider mounting tab between the vertical legs of the H-shaped openingand on the side of the cross member of the H-shaped opening farthestfrom the rigid beam, the H-shaped opening defining a rectangular loadpoint tab between the vertical legs of the H-shaped opening and on theside of the cross member of the H-shaped opening closest to the rigidbeam, the load point tab being of reduced material thickness and havinga load supporting protrusion located closely adjacent the cross memberof the H-shaped opening, the flexure mounting surface, compliant beams,rigid beam and gimbal section all formed from a single contiguous pieceof resilient material, and an air bearing slider attached to the slidermounting tab.
 19. An assembly as claimed in claim 18 wherein the loadsupporting protrusion directly contacts the slider.
 20. An assembly asclaimed in claim 19 wherein the slider is substantially centered withinthe gimbal section.
 21. An assembly as claimed in claim 20 wherein theslider has substantially the same length and width as the H-shapedopening.
 22. A flexure as claimed in claim 1 wherein the rigid beam isin the form of a truncated acute isosceles triangle, with the base ofthe triangle attached to the compliant beams and the sides formed out ofplane in the shape of channels.
 23. A disc drive magnetic head mountinggimbal comprising a load point button formed by partially etching awaysurrounding material.
 24. An disc drive magnetic head mounting flexurewith integral gimbal comprising: a load beam; a first tab integral withsaid load beam having an integral button formed by an etching process,said button facing a first, head direction; a second tab longitudinallyspaced from said first tab the second tab providing a head mountingsurface in said head direction; and a pair of partially etched beamsconnecting said first and second tabs.
 25. A method of making the discdrive magnetic head mounting flexure of claim 1 comprising:through-ecthing an H-pattern at the end of a load beam to define thetabs and connecting beams; half-etching from the head direction thefirst tab after first having masked the button area so that it remainsunetched; and half-etching said connecting beams from a seconddirection, opposite said head direction.
 26. The method of making thedisc drive magnetic flexure of claim 25 further including: forming aslight bend in the first tab towards said head direction.
 27. The methodof making the disc drive magnetic flexure of claim 25 furthercomprising: forming a radius on the load button.
 28. The method ofmaking the disc drive flexure of claim 25 further including:through-etching a head observation hole in said first tab adjacent saidload beam.